Process for the production of thiocyano derivatives



Patented Aug. 4, 1931 UNITED STATES PATENT OFF-ICE EDWARD LESLIE HELWIG,OF BRISTOL TOWNSHIP, BUCKS COUNTY, PENNSYLVANIA PROCESS THE PRODUCTIONOF THIOGYANO DERIVATIVES No Drawing.

This invention relates to the roduction -of the thiocyano derlvativesaromatlc compounds. In the past it has been customary to preparethiocyano derivatives by the action of a halogen on a mixture of analkali thiocyanate and the compoundwhose thiocyano I derivative was tobeprepared. This method 4 of free halogen tends to accelerate the polyl Iby. the action of thiocyanogen on the commerization of thiocyanogen.With the more expensive halogens, bromine and iodine, the yield isconsiderablyjbetter but the recovery of the halogens is not easy andthus the process becomes quite expensive.

These derivatives have also been prepared pound in an inert solvent.This is also not very satisfactory due to the rapid polymerizatlon ofthe thiocyanogen.

I have found that these thiocyano derivatives can be very convenientlyprepared in good yields electrolytically. The compound whose thiocyanoderivative is to be prepared, sometimes known as the depolarizer, ismixed with a soluble thiocyanate or thiocyanic acid and electrolyzed,using an insoluble anode.

It is usually not necessary to use a diaphragm although it is advisablewherethe compound desired is easily reducible.

Cooling the electrolyte has been found to increase the yield.

In most cases, alcohol has been added to the electrolyte to increase thesolubility of theconipound whose thiocyano derivative is to be prepared,and in some cases to prevent freezing at the low temperatures.

employed.

The current densit is so regulated that the thiocyanogen is' iberatedonly so rap- Application filed October 3, 1929. Serial No. 397,163.

idly as it can be taken up by the compound, whose thiocyano derivativeis to be prepared, as otherwise it is wasted either by further oxidationor by polymerization. In the absence of said compound the bulk of thethiocyanogen polymerizes as it is liberated As the concentration of thesaid compound drops off towards the end of the reaction, it isfrequently advisable to reduce the current density somewhat to preventwasting thiocyanat.

It is not necessary to restrict the work to quali cations being that theelectrode must not oxidize the thiocyanogen or the compound used too farnor be attacked itself. Any cathode material may be used which will notreduce the desired thiocyano derivative, and even this restriction isremoved if a diaphragm is employed.

I have obtained the best results when applying my invention to theproduction of para-thiocyano derivatives, although it may be adapted tothe production of meta and ortho derivatives.

articular anode material, the only" The following examples will serve toillustrate the nature of the invention but the invention is notrestricted to the examples.

The proportions are by weight.

Emample J. The preparation of gram-thiocyano-ortho-toluidine Thefollowing electrolyte is made up:

20 parts sodium thiocyanate, 35 parts water, 25 parts hydrochloric acid(35%), 25 parts ethyl alcohol (95%), 12 parts ortho-toluidine. This iselectrolyzed between a rotating graphite anode and a copper cathode. Thecell is cooled to 0 C.+ 5 C. The anode current density is maintained atabout 2 amperes per square decimeter. When 1.25 times the theoreticalamount of current, measured as ampere hours or any other units, haspassed through the cell, the current is interrupted. The electrolyte isfound to contain a yield of 75% of the product, based on the toluidinetaken, showing a" current efiiciency of 60%.

'- H. Kersteln & R. Hofimaim-Ber.. 57pages 491-196.

Wan- 2. The preparation of para-thiocyano-dimethg lam'line The followingelectrolyte is made up:

37 parts ammonium thiocyanate, 95 parts water, 50 parts ethyl alcohol(95% partsdimethylaniline .38 parts hydrochloric acid (35%). The eectrolyte 1s cooled to C. and, while being circulated by means m of acentrifugal pum is electrolyzed between stationary grap ite'anodes andcopper cathodes. An anode current densltypf 2 to 3 amperes per squaredecimeter 1s ma1n-.

tained and 1.2 to 1.4 times the theoretical amount of current is passedthrough the cell.- 75% of the dimethylaniline 1S converted the thiocyanoderivative.

Example 3.- The ,preparation of .Z-amino 5-thz'ocyano beneoz'e aeil- Thefollowing electrolyte is made up:

parts sodium thiocyanate, 17 parts water, 21 parts hydrochloric acid(-35%), 35 parts methyl alcohol, 14 parts anthranilic acid. This iselectrolyzed between a ro- 25 tating graphite anode and a stationaryaluminum cathode, using an anode current density of 1.0,to 1.5 amperesper square decimeter, the. temperature being maintained around +5 C. 1.5times the theoretical amount of current is used. 60% of the anthranilicacid is converted to the thiocyano derivative. Example 4. Thepreparation of J-amino .l-thz'oeyano naphthalene 34 parts of a 76%solution of calcium thiocyanate are treated with 60 parts -of 20%sulphuric acid in the cold. The calcium sulphate so formed is filteredoff and Ewample .4 washed with 35 parts methyl alcohol. To

the filtrate and washings, 15 parts alphanaphthylamine are added. Theelectrolyte is cooled to 0 C. and electrolyzed between a rotatinggraphite anode and an aluminum cathode; a' current density, of 1.5amperes per square decimeter being maintained.

1 Twice the theoretical current is passed throughthe cell. A yield of%55% is obtained, based on the alpha-naphthylamine 50 taken.

Example 5. The preparation of I parathioeyano-ortho-eresol The followingelectrolyte is made up: 20' parts sodium thiocyanate, 27 parts water, 25parts hydrochloric acid (35%), 36 parts methyl alcohol, 11 parts orthocresol. This is electrolyzed between a. ro-

tating graphite anode and an aluminum cathode, using a current densityof 2 amperes per square decimeter, until 1.5 times the theoreticalcurrent is passed. The.temperature is maintained at -5 C. A yield ofapproximately 40% is obtained, based on the cresol taken.

Emample 6. Thz'ocyano resorcinol 25 parts calcium thiocyanate solutionare treated with 63 parts sulphuric acid "20% and the calcium sulphatefiltered oil.

current density of 1.5 amperes per square decimeter at. 0 C. until thetheoretical amount of current has passed through the.

cell. ,A yield of 60% thiocyano-resorcinol is obtained, based on .theresorcinol taken.

I Eat-ample "7. Thioeyano resorcinol '12 parts resorcinol and 20 partssodium thiocyanate are dissolved in 60 parts water.

- This solution is placed in the anode compartment of a divided cell. 5%sodium hydroxide solution is placed in the cathode compartment.' Arotating graphite anode and copper cathode are used. An anode currentdensity of 1 to 2 amperes per square decimeter is maintained until thetheoretical amount ofcurrent has been used. The anolyte then contains50-60% of the theoretical amount of thiocyano-resorcinol.

Example 8. Thz'oayano phenol 14 parts of 88% phenol and 20 parts sodiumthiocyanate are dissolved in 15 parts of ethyl alcohol and 35 partswater, This solution is placed in the anode compartment of a dividedcell. 10% sodium hydroxide solution is placed in the cathodecompartment. A rotating graphite anode and copper cathode are used. Ananode current density of 1 ampere per square decimeter is maintaineduntil the theoretical amount of current has been used. The temperatureis kept between 0 C. and 13" C, At the end of the electrolysis, theanolyte is found to contain 25% of the theoretical amount of thiocyanophenol.

Having thus described the nature and objects of my invention andillustrated specific embodiments of the same, what I claim as new anddesire to secure by Letters Patent is 1. A process for the productionofthiocyano derivatives of organic compounds which comprises mixing thecompound whose derivative is desired with a substance capable ofyieldingthiocyanogen ions and pounds which comprises mixing the compoundwhose derivative is desired w1th a substance capable of yieldingthiocyanoggn ions and electrolyzing the mixture.

4. A process for the production of the thiocyanoderivatives of anaromatic compound of the roup consisting of amines "and phenols 'w ichcomprises mixing the rivative is desired with a substance selected fromthe group consisting of thiocyanates, thiocyanic acid and a substancecapable of producing thiocyanic acid and electrolyzing the mixture.

7. A process for the production of thiocyano derivatives of aromaticcompounds which comprises mixing the compound whose derivative isdesired with a substance selected from the group consisting ofthiocyanates, thiocyanic acid and a substance capable of producingthiocyanic acid and electrolyzing the mixture.

8. A process for the production of parathiocyano derivatives of aromaticcompounds which comprises mixing the compound whose derivative isdesired with a substance selected from the group consisting ofthiocyanates, thiocyanic acid and a substance capable of producingthiocyanic acid and electrolyzing the mixture.

9. A process for the production of thiocyano derivatives of an aromaticcompound of the group consisting ofamines and phenols which comprisesmixing the compound whose derivative is desired with a substanceselected from the group consisting of thiocyanates, thiocyanic acid anda substance.

capable of producing thiocyanic acid and electrolyzing the mixture.

10. A process for the production of parathiocyano derivatives of acompound of the group consisting of amines and phenols which comprisesmixing the compound whose derivative is desired with a substanceselected from the group consisting of thiocyanates, thiocyanic acid anda substance capable of producing thiocyanic acid and electrolyzing themixture.

11. A process for the production of thiocyano derivatives of organiccompounds which comprises mixing the compound whose derivative isdesired with a substance capable ofyielding thiocyanogen ions and belowabout 5 C.

12. A process for the production of thiocyano derivatives of organiccompounds vwhich comprises mixing the compound Whose derivative isdesired with a substance selected from the group consisting ofthiocyanates, thiocyanic acid and a substance capable of producingthiocyanic acid and electrolyzing the mixture at a temperature belowabout 5 C.

13. A process for the production of thiocyano derivatives of aromaticcompounds which comprises mixing the compound whose derivative isdesired with a substance capable of yielding thiocyanogen ions andelectrolyzing the mixture at a temperature below about 5 C.

14. A process for the production of parathiocyano derivatives ofaromatic compounds which comprises mixing the compound whose derivativeis desired with -a substance capable of yielding thiocyanogen I ions andelectrolyzing the mixture at a temperature below about 5 C.

15. A process for the production of the thiocyano derivative of anaromatic compound of the group consisting of amines and phenols whichcomprises mixing the compound whose derivative is desired with asubstance capable of yielding thiocyanogen ions and electrolyzing themixture at a tem perature below about 5 C. 16. A process for theproduction of the para-thiocyano derivative of a compound of the groupconsisting of amines and phenols which comprises mixing the compoundwhose derivative is desired with a substance capable of yieldingthiocyanogen ions and electrolyzing the mixture at a temperature belowabout 5 C.

17. A process for the production of thiocyano derivatives of organiccompounds which comprises mixing the compound whose derivative isdesired with a substance capable of yielding thiocyanogen ions and analcohol and electrolyzingthe mixture at a temperature below about 5 C18. A process for the production of parathlocyano derivatives ofaromatic com-,

pounds which comprises mixing the compound whose derivative is desiredwith a substance capable of yielding thiocyanogen lons and an alcoholand electrolyzing the mixture at a temperature belowabout 5 C.

19. A process for the production of thiocyano derivatives of organiccompounds WhlCh comprises mixing the compound whose derivative isdesired with a substance capable of yielding thiocyanogen ions andelectrolyzing the mixture while maintaining an anode current densitybetween about 1 amp. and 3 amps. per square decimeter of anode surfaceand while cooling the electrolyte. 1

electrolyzing the mixture at a temperature 20. A process for theproduction ofthiocyano derivatives of aromatic compounds which comprisesmixing the compound,

capable of yielding thiocyanogen ions and electrolyzing the mixturewhile maintaining an anode current density of between 1 about 1 amp. and3 amps. per square decimeter of anode surface and while cooling theelectrolyte.

22. A process -for the production of thiocyano derivatives of. organiccompounds which comprises mixing the compound whose derivative isdesired with a substance selected. from the group consisting ofthiocyanates, thiocyanic; acid, and a substance capable ofproducing'thiocyanic acid and electrolyzing the mixture whilemaintaining an anode current density of between about 1 amp. and 3 amps.per square decimeter of anode surface and while cooling the electrolyte.

23. A process for the production of thiocyano derivatives of organiccompounds. which comprises mixing the com- 0 C. while maintaining ananode current density ofabout '1.5 amp. per square decimeter of anodesurface.

28. A processforvthe production of 2- amino, fi-thiocya'no benzoic acidwhich comprises mixing anthranilic acid with a substance capable ofyielding thiocyanogen I ions and electrolyzing the mixture.

29. A process for the production of 2- I amino, 5-thiocyano benzoic acidwhich comprises mixing anthranilic acidwith a thiocyanate andelectrolyzing the mixture at a temperature of about 5C. whilemaintaining an anode-current'density of between 1 and 1.5 amps; persquare decimeter of anode surface.

' In testimonywhereof l have hereunto set my hand. 1

- =EDWARDLESLIE HELWIG.

pound whose derivative is desired with a substance capable of yieldingthiocyanogen ions and electrolyzing the mixture at a temperature belowabout 5 C. .while maintaining an anode current density of between about1 amp; and 3 'amps. per square decimeter of anode surface.

24:. A pro ess for the production of para--' thiocyano-dimethylanilinewhich comprises mixing adimethylaniline salt with :a substance capableof yielding thiocyanogen ions ,."mixing the hydrochloride ofdimethylaniline 4 cyano-resorcinol which and electrolyzing the mixture.

25. A process for the production of para thiocyano-dimethylaniline whichcomprises with ammonium thiocyanate and electrolyzing the mixture at atemperature of about 0 C. while maintaining an anode current density offrom 2 to 3 am s. r uare decimeter of anode surface. p pe 26. A processfor the production of thiocyano-resorcinol which comprises resorcinolwith a substance capable of yieldmg thiocyanogen ions and electrolyzingthe mixture. y

27. A process for the production of thiocomprises mixing resorcinol withthiocyanate and electrolyzmg the mixture at a temperature of about

